1. Field of the Invention
The present invention relates to a piezoelectric vibrator and an electrode structure of the piezoelectric vibrator, and more particularly, to an electrode structure of a piezoelectric vibrator reducing the manufacturing cost and having high reliability.
2. Description of the Related Art
In general, a piezoelectric vibrator is widely used for a frequency oscillator, a frequency regulator, and a frequency converter. This piezoelectric vibrator uses a crystal having excellent piezoelectric characteristics as a piezoelectric material. In this case, the crystal serves as a stable mechanical vibrating generator.
In this case, the crystal used as a piezoelectric material is artificially grown in an autoclave under high pressure, and manufactured into a wafer form by being cut off from a crystal axis so as to have a desired characteristic. In this case, the crystal must be formed to have a low phase noise, a high quality (Q) value, and a low frequency variation rate with respect to time and environmental changes. The Q value is a value representing a band selection characteristic in a resonator, filter, and oscillator, and also referred to as a Quality Coefficient. The Q value can be obtained from a ratio of a center frequency to a bandwidth of 3 decibel dB. If the Q value becomes greater, the oscillator has a more excellent frequency selection characteristic.
FIG. 1 is a cross-sectional view illustrating a piezoelectric material and an electrode structure of a related art piezoelectric vibrator. FIG. 2 is a cross-sectional view illustrating a related art piezoelectric vibrator package. Referring to FIG. 1, the related art piezoelectric vibrator 10 includes a piezoelectric material 11, and first and second electrodes 12a and 12b. The piezoelectric material 11 is formed of a crystal piece. The first and second electrode 12a and 12b are oppositely formed on the upper surface and the undersurface of the piezoelectric material 11, respectively. This piezoelectric vibrator 10, as described in FIG. 2, may have a package structure for usage. A related art piezoelectric vibrator package includes a bottom layer 16a, first and second electrode pads 14a and 14b formed on the bottom layer 16a, a piezoelectric material 11 having one side thereof fixed on the first and second electrode pads 14a and 14b, and a bump 15 arranged between the upper surface of the bottom layer 16a and the other side of the piezoelectric material 11. In this case, as described above, the first and second electrodes 12a and 12b electrically connected to the first and second electrode pads 14a and 14b may be formed on the upper surface and the undersurface of the piezoelectric material 11. A support layer 16b forming a spatial portion accepting the crystal piece 11 is formed on the peripheral portion of the bottom layer 16a. Also, a lead 17 may be arranged on the support layer 16b to seal the spatial portion.
Generally, the first and second electrodes 12a and 12b are formed of Au having high physical and chemical stability. However, because Au is expensive, Au becomes a factor increasing the manufacturing cost in an electrode structure requiring an enough thickness, and also has a limitation of low adhesive strength to the piezoelectric material 11.